Alkylation of isoparaffinic hydrocarbons



Patented Jan. 4, 1944 ALKYLATION OF ISOPARAFFINIC HYDROCARBON S Louis S.Kassel, Chicago, Ill., assignor to Universal Oil Products Company,Chicago, 111., a corporation of Delaware Application December 29, 1941,Serial No. 424,768

14"Claims.

This invention relates to the treatment of isoparafllnic orbranched-chain paraflinic hydrocarbons to'produce therefrombranched-chain paraiilnic hydrocarbons of higher molecular weight. In amore specific sense this invention is concerned with a novel process foralkylating isoparafllnic hydrocarbons comprising isobutane andrelatively low boiling normally liquidbranched-chain paraflinswithnormally gaseous or liquid olefins to produce therefrom normallyliquid saturated hydrocarbons which may be utilized as components ofgasoline suitable for use in airplane or automobile engines.

The cracking process, which is operated principally with the object ofproducing gasoline from heavier and less valuable petroleum fractionsincidentally produces considerable yields of fixed gases consisting ofhydrogen, methane, ethane, propane, and butanes, as well as ethylene,propene, and butenes in varying quantities and proportions. In mostinstances, these gases are considered to be valuable merely as fuel,although attempts have been made from time to time to utilize theolefinic constituents for the manufacture of hydrocarbon derivatives ona commercial basis.

In one application of the present process the isobutane and olefinspresent in cracked gas mixtures are utilized as a source of additionalyields of motor fuel fractions to augment those produced primarily bycracking. While the process is particularly applicable to theutilization of the hydrocarbons in cracked gas mixtures and in selectedfractions produced therefrom in the stabilizers of cracking plants,it'is also applicable to the treatment of branched chain parafdns andoleflns produced from any other source. Eiforts to alkylate normalparaflln hydrocarbons with oleilns in the presence of catalysts havethus far failed unless concurrent isomerization of the normal tobranched-chain paraflin occurs. Isobutane is the isoparaflin commonlysubjected to alkylatlon although higher molecular weight isos also reactwith oleflns under similar or modified conditions of operation toproduce branched chain paramns of higher boiling point than thelsoparaillns charged to the process.

However, as the higher molecular weight isoparailins such as isopentane,isohexane, etc., are themselves valuable constituents of gasoline, theyare consequently used less commonly as charging stocks for thealkylation process than is isobutane. Mono-oleflns and particularlythose containing from 3 to about 16 carbon atoms permolecule areutlllzable for alkylating isoparaffins in the presence of mixedcatalysts comprising both hydrogen fluoride and sulfur dioxide, althoughthe common olefin-containing charging stocks are often limited tohydrocarbon fractions containing propene and butenes. Normal paraflinsfrequently present in hydrocarbon fractions containing propene andbutenes dilute the reacting hydrocarbons but are separable from thealkylation products by distillation. Thus propane and normal butane maybe removed from the alkylation product while an isoparaflin such asisobutane, which is also separated from the reaction product, isrecycledto further alkylation treatment.

In one specific embodiment the present inven- 1 tion comprises aprocessfor synthesizing substantially saturated hydrocarbons of gasoline.

boiling range by alkylating isoparaillnic hydrocarbons with olefinichydrocarbons in the presence of a composite of liquid hydrogen fluorideand sulfur dioxide,

Whereas previousv work in alkylating various classes of parafilns witholeflns indicates that the reactions can be brought about in thepresence of composites containing boron fluoride, hydrogen fluoride andnickel and in the presence of mixtures of hydrogen fluoride and sulfuricacid, these alklylation reactions are brought about more effectively bythe process of the present invention utilizing as catalyst a compositeof hydrogen fluoride and sulfur dioxide. Since bydrogen fluoride boilsat about 20 C, and sulfur dioxide at about --10 C., mixtures of thesetwo materials may be handled readily as liquids under a relatively lowsuperatmospheric pressure,

generally not more than about 20 atmospheres or even at atmosphericpressure when the reaction mixture is cooled to a temperature below thenormal boiling point of the catalyst components and hydrocarbons chargedto alkylation,

The hydrocarbon conversions which occur when an isoparailin is alkylatedwith an olefin in the presence of a catalyst involve not only simplecombinations of isoparafllns with oleilns to form branched-chain paramnsof higher molecular weight, but also some reactions of polymerizationand certain amounts of decomposition so that the net result is theproduction oramixture of substantially saturated hydrocarbons having aconsiderable boiling range but containing a large proportion ofalhylated hydrocarbons boiling within the range of gasoline and having arelatively high an ock value. Polymerization is kept relatively low whena moderate excess of isoparamn to olefln'is maintained throughout theentire reaction. While the normal ratio of isoparafiins to mono-oleflnichydrocarbons may be as low as about 1 or as high as about 10, with apreferred ratio of about 5, the exact ratio of isoparanin to olefin forgood operation depends bon charge rates generally require a greaterfluorides or other fluorine-containing compounds,

whereas the use of catalyst mixtures containing relatively large amountsof hydrogen fluoride and relatively small amounts of sulfur dioxideeffects the formation of alkylation products which are substantiallyfree from fluorine-containing com pounds. It is therefore seen thatcatalyst com-- posites containing different proportions of hydrogenfluoride and sulfur dioxide are not necessarily equivalent in theiraction and that the catalyst activity can be controlled within certainlimits by the choice of the proportions of hydrogen fluoride and sulfurdioxide used in the catalyst composites.

The alkylation of isoparafiinic hydrocarbons amount of mixing.Indications by which un-' favorable operating conditions may berecognized are usually the production of a less completely saturatedproduct and the presence of excessive amounts of alkyl fluorides in theproduct. The

results can then be improved in most cases by reducing the charge rateor by increasing the mixing. An unnecessarily high extent of mixing, atleast within moderate limits, does not have a markedly harmful effect onproduct quality. With these general rules as a basis, it is easy todetermine optimum conditions for any particular charging stock.

While the alkylation of isobutane with oleflns in the presence of acomposite catalyst comprising hydrogen fluoride and sulfur dioxide isnot understood completely, it is believed that the.

catalyst is miscible with the hydrocarbons present in the alkylationreaction mixture since it is known that the C3 and C4 hydrocarbons aremiscible with sulfur dioxide at alkylation temwith olefinic hydrocarbonsin the presence of a mixture of hydrogen fluoride and sulfur dioxide ispreferably carried out at temperatures between about 0 and about 50 (3.,although satisfactory results are also obtainable at temperatures as lowas about -30 C. and as high as about 100 C.

alkylation reaction mixture is generally main- 3 tained under asuperatmospheric pressure of up to about 20 atmospheres when alkylatingthe lower-boiling isoparafiins, as isobutane o'r isopentane by normallygaseous oleflns, but these operating conditions may be altered whencarrying out similar reactions between higher boiling isoparafllns andoleflns of varying structures. Superatmospheric pressures are generallyused which are suflicient to maintain the hydrocarbons and catalyst insubstantially liquid state or to effect liquefaction of a portion of thereaction mixture including the catalyst.

The amount of hydrogen fluoride-sulfur dioxide composite catalystemployed is preferably from about 10 to about 100 parts by weight ofcatalyst per 100 parts by weight of hydrocarbons undergoing treatment atany one time, although in some operations other ratios of catalyst tohydrocarbon mixtures may be used.

The charge rate, expressed as volumes of hydrocarbon per volume ofhydrogen fluoride in the reactor per hour, and the amount of mixing inthe reactor are two important variables which are suitably correlatedwith each other, as well as with other process variables in order toobtain best results. The charge rate isordinarily between about 0.5 andabout 20 volumes of by drocarbons per volumecf catalyst mixture perhour; other things being equal, higher hydrocar peratures and thatsulfur dioxide is also miscible with hydrogen fluoride at thesetemperatures. This miscibility of the catalyst with the hydrocarbonstherefore appears to be a factor favoring alkylation since theconcentrations of hydrocarbons are accordingly increased in the regionswhere alkylation occurs. I

The process of the present invention may be carried out in either batchor continuous types of operation. In a simple batch process anisoparaflin to be alkylated, such as isobutane, is brought to thealkylation temperature within the approximate range specified and in thepresence of the necessary amount of catalyst mixture, and alkylation iseffected by the gradual introduction thereto of an olefin, or preferablyof an olefinisoparallin mixture while the mixture is stirredmechanically to effect intimate contact between the catalyst and thereacting hydrocarbons. The mixture of alkylation products and catalystcomposite is removed periodically from the batch type reactor andfractionally distilled to separate a mixture of unreacted isoparailinsand catalyst from higher boiling alkylation products of gasoline boilingrange. The recovered mixture of unreacted isoparaflin and used catalystis returned to further use in a later run for alkylation of anadditional quantity of an isoparaflin with an olefin.

It is usually preferable to carry out the alkylation reactioncontinuously by withdrawing from the alkylation reactor a complexmixture of excess unreacted isoparafllns and admixed normal parafiins,an alkylate of gasoline boiling range,

- higher boiling hydrocarbons, and catalyst composite, said complexmixture being withdrawn at substantially the same rate as that at whichthe hydrocarbons and catalyst are'supplied to the alkylation reactor. Asthe process is usually opgrated, sufficient pressure is maintained uponthe reaction mixture to keep a substantial proportion thereof in liquidstate. The exact pressure necessary depends both upon the composition ofthe reaction mixture and the temperature employed. The alkylationreactor used in the process consists quite-often of a coil or towerprovided with bailles, orifice plates or other mixing devices, or avessel provided with a stirrer or other mechanical means of agitation,although any method may be employed which satisfactorily effectsintimatecontact of the reacting hydrocarbons and cataltit yst compositeemployed. It may sometimes be and the flow may be'either in series or inparallel.

The accompanying diagrammatic drawing shows one specific arrangement ofinterconnected apparatus units which may be used in carrying out theprocess of this invention, although alternatively other types ofapparatus may also be employed.

Referring to the drawing a butane fraction containing a relatively highproportion of isobutane is introduced through line I and valve 2 to pumpor compressor 3 which discharges through line 4 and valve 5 into reactor6. Another hydrocarbon fraction containing both butanes and butenes isadmitted through line I and valve 8 to pump or compressor 9 whichdischarges through line 10 and valve H into line 4 already mentionedthrough which the mixture of isobutane and normal butane -is introducedinto reactor 6. The liquid catalyst mixture used in the process andconsisting of both hydrogen fluoride and sulfur dioxide is introducedthrough line l2 and valve to pump l4 which discharges through line l5,valve l6, and lines l0 and Q 4 to reactor 6. Reactor 6 comprises avessel of suitable construction for carrying out the process. Thereaction mixture contained in reactor 6 is mixed by means of stirrer lloperated by a motor, or other prime mover 18. The mixture ofhydrocarbons and catalyst is continuously withdrawn from reactor 6through line I9 and valve 20 to fractionator 2| of conventional designin which vapors of unconverted isobutane and the mixed hydrogenfluoride-sulfur dioxide catalyst are removed and directed therefromthrough line 22, valve 23, condenser 24, run-down line 25, and valve 26to receiver 21 provided with conventional gas release line 28 containingvalve29. From receiver 21 the liquefied mixture comprising essentiallyunconverted isobutane, hydrogen.

fluoride, and sulfur dioxide may be withdrawn therefrom through line 30and valve 3|. However, the major proportion of the liquefied materialcollected in receiver 21 is withdrawn therefrom through line 22 andvalve 33 by pump 34- which discharges through line 35 and valve 24 intoline 4, already mentioned. In this way the recovered mixture ofunconverted.isobutane and catalyst is recycled to further use in reactor6.

The normally liquid alkylation product admixed with normal butane, thelatter present in one or both of the hydrocarbon fractions charged tothe process, is directed from near the bottom of fractionator 2| throughline 21 and valve 28 to pump 30 which discharges through line and valve4| into fractionator 42 of conventional design in which hydrocarbonmixture introduced. thereto is separated into a normal butane fraction,a substantially saturated alky-.

late of gasoline boiling range (containing a substantial amount ofbranched chain octanes) and a mixture of higher boiling hydrocarbons.The mixture introduced to fractionator 42 may also contain relativelysmall amounts of hydrogen storage or other use not illustrated in theattached diagrammatic drawing. The lowerhydrogen fluoride layer iswithdrawn from sepa-- and catalyst is recycled to further alkylationtreatment.

From fractionator 42 vapors of a substantially saturated alkylate ofgasoline boiling range are directed through line 56, valve 51, condenser54, and the condensate is passed through run-down line 59, and valve 60to receiver 6| provided with conventional gas release line 62containing. valve 63, and with liquid draw-off line 64 containing valve65. The substantially saturated alkylate, which is the desired productof the process, is withdrawn through line 64 and valve 4' to storage.Alkylation products boiling higher than the desired gasollne fractionare withdrawn from the bottom of fractionator 42 through line 68 andvalve 61 to cooling and storage not shown in the diagrammatic drawing.

The following example is given to indicate results obtained by the useof the present process, although it is not intended to limit thegenerally broad scope of the invention in exact correspondence with thedata given.

A mixture of grams of liquid hydrogen fluoride and 80 grams of sulfurdioxide was placed in a nickel-lined autoclave of 1100 cc. capacityprovided with a motor driven stirrer. The autoclave and catalyst mixturecontained therein cent higher boiling hydrocarbons. The resultantreaction mixture, which was under a pressure of 4.5 atmospheres, wasthen stirred for an additional hour, after which the product was stabi--lized to remove a substantial proportion of the unconverted gaseoushydrocarbons and catalyst from higher boiling alkylation products. Therecovered unconverted gaseous hydrocarbons consisted of 0.6 per cent ofpropane and 99.4 per cent of butanes. The higher boiling alkylationproduct, after washing with alkali and water, and drying, amounted tograms, a yield of 152 per cent based upon the weight of the propeneconverted.

, The stabilized, washed, and dried hydrocarbon product was separated bydistillation into the following fractions:

- Boilin Volume Fraction No. point 0% Format 1 20-78 a Z 8%?) I:iii'dl'l "III Above 100 as Thus more than 60 per cent of the normallyliquid alkylation product consisted of heptanes, probably2,2-dimethylpentane and 2,4-dimethylpentane. The residue boiling above100 0. contained some unsaturated hydrocarbons and also small amounts ofcomponds containing fluorine.

The foregoing specification and example serve to indicate the characterof the process of the present invention and the nature of the resultsobtained therefrom, although neither section is an olefin in thepresence of a mixture of hydrogen fluoride and sulfur dioxide.

2. A process for producing liquid hydrocarbons mixture of hydrogenfluoride and sulfur dioxide.

from hydrocarbon gases which comprises alkylating a normally gaseousisoparaflln with a normal.-

ly gaseous olefin in the presence of a mixture of hydogen fluoride andsulfur dioxide.

3. A' process for producing hydrocarbons boiling in the gasoline rangewhich comprises alkylating isobutane with a normally gaseous olefin inthe presence of a mixture of hydrogen fluoride andsulfur dioxide.

4. A process for producing heptanes which comprises alkylating isobutanewith propene in the presence of a mixture of hydrogen fluoride andsulfur dioxide.

5. A process for producing octanes which comprises alkylating isobutanewith a butene in thepresence of a mixture of hydrogen fluoride andsulfur dioxide.

6. A process for converting normally gaseous hydrocarbons into normallyliquid substantially .saturated hydrocarbons of relatively highermolecular weight which comprises alkylating a normally gaseousisoparaffln with a normally gaseous monoolefin in the presence of amixture of hydrogen fluoride and sulfur dioxide while maintaining thereactants in essentially liquid state.

.7. A process for producing substantially saturated hydrocarbons havingmolecular weights suitable for use as motor fuel constituents whichwhich comprises alkylating an isoparaflln of relarelatively lowmolecular weight in the presence of a mixture of hydrogen fluoride andsulfur dioxide at a temperature between about 30 and about 8. A processfor producing substantially saturated hydrocarbons having molecularweights suitable for use as motor fuel constituents which comprisesalkylating an isoparaflln of relatively low molecular weight withamono-olefin of relatively low molecularweight in the presence of amixture of hydrogen fluoride and sulfur dioxide at a temperature betweenabout 30 and about 100 C. undera'pressure sufficient to maintain inliquidstate .a substantial proportion of the reacting hydrocarbons andmixture of hydrogen fluoride and sulfur dioxide.

tively low molecular weight with a mono-olefin of j 9. A process forproducing heptanes which comprises alkylating isobutane with propene inthe presence of a mixture of hydrogen fluoride and sulfur dioxide at atemperature between about 30 and about 100 C. under a pressuresufficient to maintain in liquid state a substantial proportion of thereacting hydrocarbons and 10. A process for producing octanes whichcomprises alkylating isobutane with isobutene in the presence of amixture of hydrogen fluoride and sulfur dioxide at a temperature betweenabout 30 and about 100 C. under a pressure suflicient to maintain inliquid state a substantial proportion of the reacting hydrocarbons andmixture of hydrogen fluoride and sulfur dioxide.

11. A process for producing octanes which comprises alkylating isobutanewith normal butenes in the presence of a mixture of hydrogen fluorideand sulfur dioxide at a temperature between "about .-30 and about 100 C.under a pressure suflicient to maintain in liquid state a substantialproportion of the reacting hydrocarbons and mixture ofhydrogen fluorideand sulfur dioxide. 12. A process for synthesizing substantiallysaturated hydrocarbons of gasoline boiling range which comprisessubjecting at least one molecular proportion of an isoparafllnichydrocarbon and one molecular proportionof an oleflnic hydrocarbon tocontact under alkylating conditions in the presence of a mixture ofhydrogen fluoride and sulfur dioxide. 7

13. A process for synthesizing substantially saturated hydrocarbons ofgasoline boiling range which comprises subjecting at least one molecularproportion of an isoparaflinic hydrocarbon and one molecular proportionof an oleflnic hydrocarbon to contact at a temperature between about-30and about 100 C.-in the presence of admixture of hydrogen fluoride andsulfur dioxi e.

I 14. A process for synthesizing substantially saturated hydrocarbons ofgasoline boiling range which comprises subjecting at least one molecu-'lar proportion of an isoparaflinic hydrocarbon and one molecularproportion of an oleflnic hydrocarbon to contact at a temperaturebetween about -30 and about 100 C. in the presence of a mixture ofhydrogen fluoride and sulfur dioxide and under a pressure sufllcient tomaintain in liquid state a substantial proportion of the reactinghydrocarbons and the mixture of hydrogen fluoride and sulfur dioxide.

LOUIS S.KASSEL.

